Outdated openssl (0.9) does not allow to compile at systems using OpenSSL 1.1

[hugotiburtino]

Please consider updating rust-openssl dependency to ^0.10.0 https://github.com/mattnenterprise/rust-ftp/blob/f0e4717ba721118af1522467368ae7cf3ba3e391/Cargo.toml#L34 since it is causing trouble to systems like Ubuntu 20.04, that uses currently OpenSSL 1.1.1, as it is a known issue of rust-openssl (v.g. https://github.com/sfackler/rust-openssl/issues/987)